A dramatic decline in elephant populations in the 1980s prompted the international community to ban ivory trading at the end of the decade. But more than a few loopholes remained, including the ability to import ivory to the US as hunting trophies, or if it was sourced from an animal that died of natural causes. But perhaps the most easily exploited was that which allowed the sale of ivory acquired before 1976, which inspired traders to pass off their goods as antiques for profit. Scientists have now used a form of carbon dating to determine the real age of ivory samples, with an early study revealing more than 90 percent of seized shipments came from animals that died within three years prior.

Humans tested a whole lot of nuclear bombs in the 1950s and 1960s. One of the upshots of this was the doubling of radioactive isotope carbon-14 in the atmosphere, which is in turn absorbed by plants. Because animals (and humans) eat plants, the isotope is passed onto our tissues, and because the concentration of carbon-14 is always declining, scientists can use the isotopic signatures of things like bones or tusks to gauge the age of the material.

This phenomenon, known as a "bomb carbon" signature, has been used to to estimate the age of human remains, trace cocaine trails through the Americas and identify fake whiskey, and now scientists have applied it to a stockpile of illegal ivory shipments seized between 2002 and 2014.

Samuel Wasser of the University of Washington, together with scientists from the University of Utah, studied a total of 231 ivory samples to find only a single tusk from an elephant that had died more than six years before landing in the hands of authorities. More than 90 percent of the elephants from whom the ivory came had died less than three years prior. All of which suggests that not a whole lot of old ivory is being shipped out of Africa.

"This work provides for the first time actionable intelligence on how long it's taking illegal ivory to reach the marketplace," says Lesley Chesson, study's co-author. "The answer: Not long at all, which suggests there are very well developed and large networks for moving ivory across Africa and out of the continent."

A dramatic decline in elephant populations in the 1980s prompted the international community to ban ivory trading at the end of the decade(Credit: Professor Benezeth Mutayoba, Sokoine University of Agriculture, Tanzania)

Scientists have used "bomb carbon" signatures to reveal the true age of seized ivory(Credit: Syarifah Khadiejah Syed Mohd Kamil, Malaysia Department of Wildlife and National Parks)